M13 · Hercules Globular Cluster
| Chinese name | 武仙座大球状星团 |
|---|---|
| Type | Globular cluster |
| Constellation | Her |
| RA | 16h41m |
| Dec | +36° |
| Apparent magnitude | 5.8ᵐ |
| Hemisphere | Northern |
| Best season | Summer |
| Difficulty | Easy |
| Focal length | 长焦 1000mm+ |
About
M13, the Great Hercules Globular Cluster, lies about 22,000 light-years away and is the most magnificent globular in the northern sky, containing roughly 300,000 stars. Visible to the naked eye as a hazy patch under dark skies, it has a densely packed core with chains of stars trailing from its edges. In 1974, the famous Arecibo message was beamed toward M13 from the Arecibo radio telescope. At magnitude 5.8 it is the premier globular-cluster imaging target, resolving into tens of thousands of member stars at long focal lengths. It is the most popular observing object in summer Hercules.